The present invention relates to a laminated body which includes a thermally conductive sheet for accelerating thermal conduction from a heat emitting body to a heat discharging body inserted between the heat emitting body and the heat discharging body.
In recent years, power consumption and heat emission have been increased with the performance upgrade of electronic devices, such as CPU's (central processing units) for computers. The processing performance of electronic devices deteriorates due to heat. Accordingly, it is necessary to avoid heat accumulation in electronic devices, in order to maintain the performance of the electronic device, and thus, cooling of electronic devices has become an important issue. Therefore, excellent thermal conductivity has been required for use of thermally conductive sheets inserted between an electronic device, which is a heat emitting body and a heat discharging body, such as a heat sink.
Japanese Laid-Open Patent Publication No. 10-183110 and Japanese Laid-Open Patent Publication No. 11-335472 disclose a thermally conductive sheet made of a silicone gel which contains a thermally conductive filler. This thermally conductive sheet is viscous due to the flexibility of the silicone gel. Therefore, the thermally conductive sheet can make close contact with the heat emitting body and the heat discharging body, and thus, can provide excellent thermal conductivity.
Japanese Laid-Open Patent Publication No. 2006-335957 and Japanese Laid-Open Patent Publication No. 2006-335958 disclose thermally conductive sheets made of a composition which contains a thermally conductive filler in fiber form and a polymer matrix. These thermally conductive sheets can provide excellent thermal conductivity due to the thermally conductive filler being oriented in one direction. Furthermore, an end portion of the thermally conductive filler is exposed from the thermally conductive sheet, and thus, the viscosity of the thermally conductive sheet can be reduced.
Japanese Laid-Open Patent Publication No. 7-149365 discloses a thermally conductive sheet wrapping body provided with a top cover tape and a thermally conductive sheet which is sealed in the top cover tape. Japanese Laid-Open Patent Publication No. 2002-222904 discloses a laminated body comprising a thermally conductive sheet provided with a support tape and a thermally conductive sheet which adheres to the support tape. The top cover tape and the support tape contribute to automation of the work for attaching the thermally conductive sheet to, for example, a heat emitting body using a machine, and at the same time, advantageously of making maintenance and carrying of thermally conductive sheets easy.
However, there is a problem with the thermally conductive sheets described in Japanese Laid-Open Patent Publication No. 10-183110 and Japanese Laid-Open Patent Publication No. 11-335472, such that the viscosity is high, and thus, ease of handling is low, for example, when attached to a heat emitting body and when carried. The thermally conductive sheets described in Japanese Laid-Open Patent Publication No. 2006-335957 and Japanese Laid-Open Patent Publication No. 2006-335958 have a low viscosity and a thermally conductive filler oriented in one direction, and furthermore, the thermally conductive sheets are thin, in order to lower the value of the thermal contact resistance, and therefore, it is easy for the sheets to shift in position or break when the thermally conductive sheet is attached to, for example, a heat emitting body. Therefore, a problem arises, such that it is difficult to attach the thermally conductive sheet. In addition, when a thermally conductive sheet wrapping body as that described in Japanese Laid-Open Patent Publication No. 7-149365 or a laminated body as that described in Japanese Laid-Open Patent Publication No. 2002-222904 is formed using the thermally conductive sheet described in Japanese Laid-Open Patent Publication No. 2006-335957 or Japanese Laid-Open Patent Publication No. 2006-335958, there is a problem with the thermally conductive sheet, of which the viscosity is low and which easily breaks, such that attachment of the thermally conductive sheet is difficult.